https://www.facebook.com/309721255743244/photos/a.313071212074915.65429.309721255743244/1018851468163549/?type=3&theater
CIRC ECG Challenge Response! Regarding the 64-year-old woman who presents with a severe dilated cardiomyopathy and heart failure.
Diagnosis: normal sinus rhythm, intraventricular conduction delay (cardiomyopathic QRS complex), left anterior fascicular block
- There is a regular rhythm at a rate of 84 bpm. There is a P wave before each QRS complex with a constant PR interval (0.16 sec). The P wave is positive in leads I, II, aVF, and V4-V6. Hence this is a normal sinus rhythm.
- The QRS complexes are wide (0.16 sec) and there is a morphology that resembles a left bundle branch block with a deep S wave in lead V1 (→) and a broad R wave in leads I and V6 (←).
- However, there are certain findings which are not seen with a left bundle branch block, particularly septal forces (i.e. small Q waves in leads I, aVL, V6 and septal R wave in lead V1). This is because the septal or medial fascicle which innervates the septum arises from the left bundle. The septum is the first part of the left ventricle to be depolarized and it is activated in a left to right direction, accounting for the small septal Q waves in leads I, aVL, and V6 and the septal R wave in lead V1. In this case, there are septal Q waves in leads I and aVL (^) and a septal R wave in lead V1 (v).
- Therefore this is not a left bundle branch block but rather a nonspecific intraventricular delay.
- Other findings not seen with a left bundle branch block are any left to right forces (terminal S wave in leads I and V6) and a right axis. With an intraventricular conduction delay left ventricular activation goes through the normal His-Purkinje system, but is slow.
- Since left ventricular activation is via the normal conduction system, abnormalities affecting the left ventricle can be diagnosed.
- In contrast, with a left bundle branch block left ventricular activation is via direct myocardial activation from the right ventricle and not the normal conduction system.
- Therefore abnormalities affecting the left ventricle cannot be reliably diagnosed. The axis is extremely left between -30° and -90° (positive QRS complex in lead I and negative complex in leads II and aVF).
- The two etiologies for an extreme left axis are an old inferior wall myocardial infarction in which there are Q waves in leads II and aVF or a left anterior fascicular block with an rS morphology in leads II and aVF.
- In this case, this is a left anterior fascicular block which can be diagnosed since there is no left bundle branch block.
- The QT/QTc intervals are prolonged (460/545 msec) and still slightly prolonged when corrected for the prolonged QRS complex duration (400/ 470 msec). When the QRS is this wide due to an intraventricular conduction delay there is likely an underlying dilated cardiomyopathy,
- i.e. this is a cardiomyopathic looking QRS complex. The last two QRS complexes (*) are wide (0.16 sec) and have a different morphology; they are not preceded by a P wave. These are premature ventricular complexes. Two in a row is often referred to as a ventricular couplet.
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